Studies in this laboratory have been primarily directed toward the effects of iodide on thyroid gland function; the physiological role of the thyroxine (T4) binding proteins, T4 binding globulin (TBG) and prealbumin (TBPA), in the transport and metabolism of T4 and triiodothyronine (T3), and the effect of drugs on hormone kinetics; the peripheral conversion of T4 to T3 in man; the pituitary-hypothalamic-thyroid feedback regulation of thyroid function; and, most recently, studies relating to neonatal thyrotoxicosis in the rat. Proposed further studies in these areas will be pursued. The effects of chronic pharmacological doses of iodide in children with cystic fibrosis and physiological supplemental amounts of iodide in patients with moderate iodine deficient goiter on various aspects of thyroid function will be evaluated. The effect of morphine, heroin, and methadone on various aspects of T4 and T3 metabolism in man and rat will be studied further. Since T3 is now believed to play a major role in thyroid hormone action, including regulation of pituitary-hypothamic function, the effect of propylthiouracil, a potent inhibitor of T4 deiodination, on the pituitary-hypothamic axis will be evaluated in man and rat receiving exogenous T4. The recovery of thyroid-pituitary-hypothamic function following withdrawal of long term thyroid suppression will be evaluated. Finally, a series of experiments will be carried out on the effects of chronic TRH administration on thyroid-pituitary-hypothamic function in pregnant, neonatal and adult rats.